This invention relates generally to a shear bolt coupling and a method of replacing a shear bolt and, in particular, to a shear bolt coupling and a method of replacing a shear bolt for use on an agricultural baler.
In a conventional type of agricultural baler, a feeder mechanism is operable to transport crop material collected by a pick-up device towards a plunger, which reciprocates in a bale case to form the crop material into rectangular bales. In operation, the feeder mechanism may be subjected to high overloads caused either by plugging of wads of crop material in the feeder duct or by jamming of a foreign object such as a piece of wood therein. In order to avoid structural damage to the baler upon the occurrence of a feeder obstruction, the feeder mechanism commonly is protected by a shear bolt coupling incorporated in the drive line thereof. The shear bolt coupling is composed of a first member and a second member which are interconnected by the shear bolt for, during normal operation, rotatably transmitting power therebetween. In case excessive loads are imposed on the feeder mechanism, high shear forces cause the shear bolt to fail whereby the first and second member are rotated relative to one another. As such, the drive line to the feeder mechanism is interrupted and severe damage is avoided.
Before normal operation of the baler can be resumed, the feeder mechanism has to be cleared and a new shear bolt has to be installed. However, since conventionally the movements of the feeder mechanism and the plunger are synchronized during normal operation, the first and second members must be reset correctly with respect to each other before a new shear bolt may be inserted to re-establish the drive transmitting coupling. For practical reasons, such as high resistance forces experienced in the drive line towards the feeder mechanism for example, the baler operator usually is unable to manually rotate the first or second members relative to each other in order to reset the same correctly. Most commonly, he resorts instead to manually actuating a flywheel which is incorporated between the tractor PTO and the baler main drive. As said flywheel usually is remote from the shear bolt coupling on the feeder mechanism, the operator has to wander back and forth between the former and the latter to see whether the first and second members are correctly positioned with respect to each other and to adjust the relative positions thereof if necessary. It readily will be appreciated that, if the operator could rely on the help of a second person, there would be no problem at all since in that case the operator could actuate the flywheel while said second person could insert the new shear bolt at the appropriate moment. Unfortunately, on most occasions, a second person is not immediately available, so consequently the operator nevertheless should rely on himself.
It is therefore an object of the present invention to provide an improved shear bolt coupling for agricultural balers and a method of easily replacing a broken shear bolt.